Malware Classification

A Quick Reference Cheat Sheet

Type	Self-Replicates?	Needs Host?	Network Spread?	Stealth	Primary Goal
Virus	Yes	Yes	No	Medium	Infect & spread via files
Worm	Yes	No	Yes	Low-Med	Rapid network propagation
Trojan	No	No	No	Medium	Deceive user for access
Ransomware	Sometimes	No	Sometimes	Low	Extort money via encryption
Spyware	No	No	No	High	Monitor & steal data
Keylogger	No	No	No	High	Record keystrokes
Rootkit	No	No	No	Very High	Hide & maintain admin access
Backdoor	No	No	No	High	Provide remote access
Botnet	Sometimes	No	Yes	Medium	Distributed control network
Fileless	Sometimes	No	Sometimes	Very High	Memory-only operation

Key Malware Categories

Virus: Attaches to host files. Spreads when files are shared.

Worm: Self-replicates across networks automatically. No user action needed.

Trojan: Disguised as legitimate software. Tricks users into installation.

Ransomware: Encrypts files, demands payment for decryption.

Spyware: Secretly monitors activities and steals information.

Rootkit: Hides presence while maintaining admin-level control.

Fileless: Lives only in memory (RAM). No disk footprint.

Polymorphic: Changes code signature each infection to evade detection.

APT Malware: Sophisticated, targeted attacks for long-term access.